Definitely start out with something much smaller. Especially if you haven't ever knit before! I wouldn't use any of the fuzzy, "fun" yarns to learn on, though. They're usually harder to knit with and can be frustrating even after you've learned.
I'd start off with a medium weight, inexpensive yarn. Usually acrylic is suggested for learning. You can usually pick up a skein for a dollar or two (I always start in the clearance yarn). Buy a few colors of the same type yarn and make some "swatches" to learn the stiches and the color changes so you'll be ready to tackle that afghan.
Good luck....and let us know how you're doing.